Hah! You can do it...unfortunately mine is taking much longer than I had planned, but I'm taking my time and hopefully doing everything right!
For the Gruvenparts pipe, it does seem to fit just right...that said, the engine is still on the stand and obviously hasn't been started yet to know if it seals right or not. When installing it, it feels like the OEM pipe as far as installation feel on the o-ring size which is positive. I can't say for sure, but it also looks like Gruvenparts used the OEM o-rings, where the eBay part had skinnier o-rings.
Hope this is helpful!